This invention relates to containers that incorporate separate compartments for different constituents, products, or elements, and more particularly to a blow molding process for fabricating such containers, and containers formed by the process.
As shown in U.S. Pat. No. 6,989,168 (Fahey), hereby incorporated herein by reference, a beverage container can be formed with a substantially centered upright cylindrical wall to divide the container into a primary compartment for the beverage, and an interior compartment open to the container bottom for containing a secondary food product, for example a package of cookies, food, a food bar, medicine, tablets, water purification tablets, crackers, or other products. To provide a more secure hold on the secondary product, the cylindrical wall forming the recess is stepped near the interior end of the recess, as perhaps best seen in FIGS. 2 and 6 of the patent. While this is considered to be an effective approach to providing the desired frictional engagement with the secondary product, it can be difficult to form the interior cavity when using a blow molding process to fabricate the containers.
Another processing difficulty, occasioned by the inward extension of the secondary compartment (i.e. upward in an upright container), is the tendency of the blow molding step to create a partial vacuum that holds the expanded thermoplastic firmly against the molding feature used to form the secondary compartment. This can prevent withdrawal of the molding feature, and thus prevent removal of the bottle from the mold.
An alternative approach for blow molding the containers was considered, namely to introduce a slight taper or incline in the recess to gradually reduce its diameter in the upward or inward direction. Then, the reduced-diameter region near the interior of the recess would provide the desired frictional fit. A sufficient degree of incline along the surfaces of the molding feature and the resulting compartment would have the additional advantage of facilitating removal of the expanded container from the mold after blow molding.
While workable, this approach created a conflict between two objectives: a secure frictional hold on the secondary product, aided by an axial or near-axial orientation of the secondary compartment wall; and enhancing the blow mold process, facilitated by providing a tapered secondary compartment wall.